HumidCalc 1.1.7

This application provides a comprehensive suite of weather-related calculations, enabling users to efficiently obtain indices such as the Temperature-Humidity Index (Discomfort Index), WBGT (Heat Stroke Index), Dew Point Temperature, and more from weather data.

The app calculates air conditions using dry-bulb temperature (Td) and wet-bulb temperature (Tw) obtained via devices like the Assmann Psychrometer. It also allows input of atmospheric pressure to enhance measurement accuracy. Users can perform calculations of 11 items across 13 indicators, with convenient unit conversions between Celsius and Fahrenheit, as well as SI units or Imperial/US customary measurements, simply by toggling the "Temperature Unit" setting.

The calculated items and indicators include:

• Dew Point Temperature
• Relative Humidity
• Humidity Ratio (Absolute Humidity)
  • Mass-based absolute humidity
  • Smallest unit mass-based absolute humidity
  • Volume-based absolute humidity
• Humidity Deficit
• Enthalpy
• Specific Volume
• Equilibrium Vapor Pressure
• Partial Pressure
• Boiling Point of Water
• WBGT (Estimated Value)
• Discomfort Index (Temperature-Humidity Index)

Regarding the WBGT (Estimated Value) and Discomfort Index calculations:

• The outdoor WBGT is typically computed using the formula “WBGT = 0.7 Tnw + 0.1 Td + 0.2 Tg”. However, this app estimates the Globe Thermometer Temperature (Tg) based on dry-bulb temperature (Td) because Tg input is not directly available. The estimation uses the formula: “Tg = 1.45 Td - 27.162” (with temperature in Fahrenheit).
• A strong correlation exists between Tg and Td, supported by statistical analysis of 17,376 samples showing an R² value of 0.919.
• The natural wet-bulb temperature (Tnw) is derived from the measured wet-bulb temperature (Tw) obtained via an Assmann Psychrometer, converting it to the natural state under wind speeds at or below 5 meters per second.

The Discomfort Index (DI), or Temperature-Humidity Index, is calculated using the formula: “DI = 0.4 × (Td + Tw) + 15”, with temperatures in Fahrenheit.

If users wish to obtain current atmospheric pressure, they can tap the "Weather" information button or press the "MEAS" button on compatible devices such as iPhone6s or later models.

The app allows selection of wet-bulb measurement conditions between “Normal” and “Froze” (the latter enabling settings for sub-zero wet-bulb temperatures). It accepts measurements from devices like non-draft psychrometers, such as Augusto Psychrometers; simply tap a button to display corresponding values, acknowledging that measurement accuracy may vary with different instrument types.

This app can also receive Td and Tw values from the companion app “Calculator of Air,” facilitating input of parameters like dew point temperature and relative humidity—note that this requires launching the partner app beforehand. Valid input ranges are from -30°C to 50°C (-22°F to 122°F) for temperature and 600 hPa to 2475 hPa (17.72 inHg to 73.09 inHg) for atmospheric pressure.

This application utilizes weather data sourced from OpenWeatherMap (CC BY-SA 4.0).

Disclaimer 1: Users are advised to input temperatures within a reasonable range (0°C to 40°C / 32°F to 104°F). Extreme values may lead to incorrect calculation results.

Disclaimer 2: The developer is not responsible for any damages or issues arising from the use of this application.